Microscopic Description -- Pain in Left Proximal Medial Thigh

Open biopsy shows a lesion which infiltrates the skeletal muscle.
The central portion is composed of loosely textured vascular fibroblastic tissue. The
fibroblasts display a mild
degree of cellular pleomorphism and contain occasional mitotic figures. Bordering these
areas is a zone with ill-defined bony trabeculae. Toward the periphery trabeculae mature and
form woven bone.